My invention relates to transmitter control apparatus, and particularly to transmitter control apparatus for reducing or eliminating the simultaneous transmission by two transmitters on a common communication medium or path.
A communication medium or path, such as a radio frequency channel, is frequently shared by a number of transmitters to conserve communication facilities or the radio frequency spectrum. This is particularly true where a given transmitter is operated for a relatively small amount of time. For example, a radio transmitter may be provided on each of a number of vehicles, such as a public bus, for the purpose of transmitting stored information, such as bus location, number of passengers, or some condition on the bus. The time required to transmit such information is very short, because the transmission can be done in a high speed data burst. However, if such transmissions are simultaneously made by two or more transmitters, it is likely that interference will occur, and no information will be received in usable form.
Accordingly, a primary object of my invention is to provide new and improved control apparatus for preventing simultaneous transmissions by a plurality of transmitters over a common communication medium or path.
Another and relatively specific object of my invention is to provide a new and improved control that produces repeating signals at a predetermined interval, the repeating signals causing a transmitter to transmit when a common communication medium is not in use.
Control apparatus for eliminating simultaneous transmission have been provided, but such apparatus have not always met the needs of systems where stored information or data should be or must be transmitted automatically, or should be or must be transmitted after a start action by an operator but without further action by the operator.
Accordingly, another object of my invention is to provide a new and improved control that accepts a start action at any time and that automatically continues to attempt to cause transmissions at periodic intervals, but that does not cause such transmissions until the common communication medium or path is free of other transmissions.